The crystallization mechanism in an amorphous Ge_2Sb_2Te5 (a-GST) thin-film induced by a single pulsed laser was investigated in this paper. The finite element simulation and X-ray diffraction (XRD) analysis showed that two kinds of crystallization mechanisms performed for the laser induced phase transition of a-GST, that is, the solid-state phase transition took place at a lower laser fluence while the liquid-solid phase transition occurred at a relatively high laser fluence. TEM observations showed that the microstructure in the liquid-solid phase transition was more uniform as compared to that in the solid-state phase transition because of poor atom diffusion. Crystallization characteristics at different laser fluences and film thickness were elucidated. It was found that at a lower laser fluence a thinner film had better crystallinity owing to thermal convection, while at a higher laser fluence a thicker film showed better crystallinity due to release of latent heat in the liquid-solid phase transition. These findings enable a deep understanding of ultra-fast phase transition induced by laser irradiation.
展开▼
